1. Field of the Invention
The present invention relates to a liquid discharge head, and more particularly, to an ink jet recording head performing recording by discharging ink and a method of producing the ink jet recording head.
2. Description of the Related Art
As an ink jet recording head, the one having a configuration as shown in FIG. 8F has been known. The ink jet recording head has a substrate 51 on which an ink discharge energy generating element 53 capable of being constituted by a heat element or the like, for generating energy for discharging ink is formed. In the substrate 51, an ink supply port 64 for supplying ink from outside is formed as a through hole. On the substrate 51, there is connected a member forming an ink discharge port 61 disposed so as to correspond to the ink discharge energy generating element 53 and an ink flow path 65 through which communication is established from the ink supply port 64 to the ink discharge port 61.
As a method of producing such ink jet recording head, a production method including the steps of forming an ink flow path pattern with a soluble resin, and coating the soluble resin with a coating resin layer (see U.S. Pat. No. 5,478,606). The coating resin contains an epoxy resin in a solid form at room temperature. The soluble resin layer can be removed by being dissolved after the formation of the coating resin layer, whereby a desired ink flow path is formed. According to such production method, a minute distance between the ink discharge energy generating element and the ink discharge port can be set with high precision and excellent reproducibility, whereby an ink jet recording head capable of performing high-quality recording can be provided.
Further, in such ink jet recording head, an insulating film is generally formed as a protective film for the ink discharge energy generating element and the like on the substrate. Further, in a case of using a heat element for the ink discharge energy generating element, an anti-cavitation layer such as a Ta film is provided. In connecting a resin forming the ink flow path to such substrate, there is known a method of interposing an adhesion enhancing layer made of a polyether amide resin so as to enhance the adhesion with respect to the substrate (see U.S. Pat. No. 6,390,606).
FIGS. 8A to 8F are cross-sectional schematic views showing basic production steps of an exemplary recording head adopting such prior art in a time series.
In a stage shown in FIG. 8A, a plurality of ink discharge energy generating elements 53 are formed on the surface of the substrate 51, and coated with a protective film 55. Further, on the surface of the substrate 51, a sacrifice layer 54 to be used in a later step of forming an ink supply port 64 is formed, and the back surface of the substrate 51 is entirely coated with a SiO2 film 52.
After that, as shown in FIG. 8B, front and back surfaces of the substrate 51 are coated with the polyether amide resin to form an adhesion enhancing layer 56 and a back surface patterning layer 57, and cured by baking. Then, the polyether amide resin layers are patterned. The patterning can be performed by applying a positive resist by spin coating or the like, exposing the resist to light, followed by developing, and removing the polyether amide resin layer by dry etching or the like, using the positive resist as a mask.
Then, as shown in FIG. 8C, the front surface is coated with a positive resist, followed by patterning, whereby a nozzle flow path molding material 58 is formed. Then, as shown in FIG. 8D, the molding material 58 is coated with a coating photosensitive resin (CR) 59 by spin coating or the like. An ink discharge port 61 is formed by exposing the coating photosensitive resin 59 to UV-light, Deep UV-light, or the like, followed by developing and patterning. A water repellent material 60 is formed on the coating photosensitive resin 59 by lamination or the like of a dry film.
Next, as shown in FIG. 8E, a protective material 62 is applied by spin coating or the like, and the front and side surfaces of the substrate 51 with the molding material 58, the coating photosensitive resin 59, and the like formed thereon are coated with the protective material 62. Further, the SiO2 film 52 on the back surface of the substrate 51 is etched, using the polyether amide resin 57 as a mask. As a result, a Si surface is exposed to be an etching initiation surface 63 for forming the ink supply port 64.
Next, as shown in FIG. 8F, the ink supply port 64 is formed in the substrate 51. The ink supply port 64 is formed by performing chemical etching, for example, anisotropic etching with a strong alkaline solution such as TMAH with respect to the substrate 51. When the anisotropic etching is performed from the back surface, an etching region reaches the sacrifice layer 54 on the surface, whereby the formation of the ink supply port 64 is completed. Next, the back surface patterning layer 57 and the protective material 62 are removed. Further, the molding material 58 is eluted from the ink discharge port 61 and the ink supply port 64, whereby the ink flow path 65 is formed.
In recent years, an increase in density has been required in the ink jet recording head, and there has been a demand for further refined ink flow path pattern. On the other hand, in the above-mentioned prior art, the ink flow path pattern is formed by patterning the molding material 58, and in connecting the coating photosensitive resin 59 onto the substrate 51, the adhesion enhancing layer 56 is interposed so as to enhance the adhesion therebetween. According to such production method, a finished dimension tolerance for both the molding material 58 and the adhesion enhancing layer 56 need to be considered for setting the ink flow path pattern. This restricts an increase in fineness of the ink flow path pattern. Further, there is a possibility that the finished tolerance of the adhesion enhancing layer 56 and the molding material 58 may influence compositively the adhesion and discharge performance of the coating photosensitive resin 59 and the substrate 51.
Further, according to a conventional production method, a material of a member forming a flow path wall is the same as that of a member forming a discharge port. Therefore, in selecting the material, there is a trade-off relationship as the following. That is, use of a material enhancing the adhesion with respect to the substrate becomes disadvantageous to the formation of the discharge port, and in contrast, when a material advantageous for the formation of the discharge port is selected, the adhesion with respect to the substrate is degraded.